Clamp structures with lever-type closure mechanisms are known in the art. For example, a simple toggle-link in a clamp structure is shown in U.S. Pat. No. 2,440,260. Another type of lever-actuated closure mechanism for a hose clamp is shown in French Patent 1,116,743. Commercially successful lever-type hose clamps are shown and described in applicant's own prior U.S. Pat. No. 3,475,793, the contents of which are incorporated by reference in this application. Though the lever-type clamp structures in applicant's aforementioned U.S. Patent disclosed the use of tensional spring elements in the form of lugs or folds, these folds or lugs left an opening underneath the same which had to be bridged by a separate bridging element to avoid the possibility of leakage within that area. This, in turn, increased the cost of manufacture by the need for separate parts in the form of bridging or connecting members which had to be installed manually. Economic reasons therefore normally prompted the omission of such tensional spring elements in the commercial versions of these lever-type clamp structures. Another problem noted from time to time with applicant's prior lever-type hose clamps was the unintentional opening of the lever-type closure mechanisms.